This research concerns a child who heard spoken language for the first time in his life at age three. He is a hearing child of deaf-mute parents who use only sign language in the home. Since his learning of speech did not begin until after a great deal of his cognitive maturation had taken place, the study of his development should tell us much about the process of language acquisition in younger children, where it is often difficult to separate the effects of cognitive maturation from those of the acquisition of the linguistic system itself. Confounding the situation somewhat is the fact that before he heard speech, he was already using the sign language of the deaf. But to the extent that his sign language influences his acquisition of speech, this will provide an excellent opportunity to study the structure of sign language as it attempts to realize itself in the auditory mode. An enormous and highly detailed record has been made of both his sign language and his speech, consisting of over 500 hours of audiotape and 100 hours of videotape, spread out at intervals over three years and three months. Much of this has been transcribed, noting in detail the context of his utterances. Structural descriptions of his utterances will be written on the basis of this contextual information and the process of their development investigated, tracing the respective influences of his cognitive maturity and his knowledge of sign language upon the course of his acquisition of speech.